Heater and circulator for thermostatic baths



LNE 2? (11%@ Q., Haw-mma@ Er AL HEATER AND CIRCULAOR FOR THERMOSTATICBATHS Filed April 27, 1935 In Ver? "Ofw i Mw.

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Patented Apr. 21, 1936 uNlrgn stares PATZNT OFFICE HEATER AND CRCULATORFOR THERMSTATEC BATES Application April 27, 1935, Serial No. 18,699

4 Claims.

This invention relates to thermal baths such as are used by biologists,chemists and physicists for maintaining objects immersed in the liquidat some definite temperature.

The objects of the invention are to provide a heater and circulator ofunitary self-supporting form suitable for use in an open vessel withouthaving brackets or the like extending to the walls of the vessel or tooutside supports; and to provide improvements in the construction andarrangement of a turbine circulator and heater for efficientlycontrolling the temperature of the bath.

A specific embodiment of the invention is illustrated in the drawing,wherein:

Figure 1 shows the operating unit in side elevation in combination witha thermal bath receptacle which is shown in section.

Fig. 2 is an enlarged vertical sectional detail of the heater andcirculator.

Fig. 3 is a diagram showing electric circuit connections for the heatingcoil.

'I'he heating and circulating unit is made so that it will stand inoperating position on the floor of a receptacle and unattached to theside walls thereof, and comprises a supporting frame structure havingmounted therein a central penstock tube through which the bath liquidcirculates upwardly under the action of an impeller iitted within thetube.

At the top of the tube is a head structure serving as a support for themotor, a thermometer, and a thermostat for regulating the delivery ofheat to the bath liquid. The heat is applied from a coil Wound upon thetube and surrounded by a spaced and insulated cylindrical housing whichseparates it from the bath liquid and assures that the heating effect isconcentrated upon the liquid within the tube. The function of thethermostat is to control heat delivery by the coil.

The drawing shows a bath receptacle I having inlet and overflowconnections 2 and 3 for the circulating medium, usually water, and whichserves to maintain at some xed point the temperature of an objectimmersed in the bath.

The circulating and heating unit comprises a supporting base li having acentral opening 5 in line with a tube extending upwardly from the baseand terminating at its upper end in a motor support or head l. Motor 8is bolted to the support 'I and the shaft 9 of the motor carries a rotorIIJ tting the bore of tube 6. The rotor I E) has a spiral channel II inits cylindrical surface and through which the bath liquid is driven up-Wardly when the motor is in operation. The

(Cl. 21S-39) openings I2 at the upper end of the tube 6 provideuniformly spaced radial outlets for the bath liquid.

The liquid is heated as it passes upwardly through the tube by means ofa heating coil I3 which consists of suitable resistance wire wound uponthe tube and having a plurality of connections ifi, Fig. 3, with arheostat I5 whereby more or less of the coil is rendered effective forheating purposes when a thermostatically op- 10 erated relay l5 permitsthe closing of contacts El. Those contacts are normally held closed asby a spring I8 except when the relay is energized through the closing ofa local circuit I 9 by a mercury contactor represented by the bulb 152l, and described in detail in our copending application for patent,Serial No. 18,698, filed April 27, 1935 on Thermo-regulators. Thiscontactor is carried by a bracket on the head 'I.

The coil d3 is housed within the cylindrical casing 2| which separatesit from the bath liquid and has a cap 22 at its upper end extendingtherefrom to the tube 6.

A thermometer for ascertaining the temperature of the bath liquid isindicated at 23 and is 25 supported by a bracket on the frame structurel.

The electrical connections to the motor heater and regulator are housedin an outlet box 24 mounted on top of the motor and connected to asource of current and other control devices not 30 shown in Fig. 1 bythe cable 25. For simplicity of illustration, the relay is shown asactuated by current from a battery although in actual practice we use amore complicated circuit for obtaining the desired minute relay currentfrom 35 the line circuit to the motor as described in our copendingapplication Serial No. 20,058, led May 6, 1935.

In operation of the heating and circulating unit the motor is inconstant operation and the heat is supplied at a rate to exactlycompensate for losses to the atmosphere and surrounding objects. Therate of the heat delivery by the coil is roughly regulated by thesetting of multistage switch i5, and the temperature of the bath is 45then automatically controlled by the intermittent operation oi circuitopener I 6 under control of the temperature responsive element 29.

The temperature responsive element may be set to close the local circuitI5 at some precise tem- 50 perature to a fraction of a degree. Thus heatis supplied as needed but the temperature of the bath water cannotexceed the temperature predetermined by the setting of the thermostaticregulator Z. This closing of the regulator circuit Cil actuates therelay to open the normally closed heater circuit and the constantcirculation of the bath maintains a constant temperature over the periodof operation.

Although but one specic embodiment of this invention is herein shown anddescribed, it is to be understood that details as set forth may bealtered or omitted without departing from the spirit of the invention asdefined by the following claims.

We claim:

1. A thermal bath comprising a reservoir for a bath of liquid heatingmedium, a vertically disposed tube within said reservoir having inletand outlet openings respectively located adjacent the bottom and top ofsaid reservoir,v an impeller within said tube for driving the heatingmedium through said tube, an electric heating coil surrounding saidtube, and a heat insulating jacket housing said coil and positioned toprevent direct heating of the bath outside the penstock.

2. In a thermal bath, a heating and circulating unit comprising avertical penstock tube having openings at the bottom and top thereof forcirculating the contents of said bath, an impeller in said tube havingan upwardly extending shaft, a motor carried on said tube for drivingsaid shaft, an electric heating element surrounding said penstock tube,a jacket cooperating with said tube to house said heating element, and abase frame carrying said unit.

3. A heating and circulating unit of the class described comprising asupporting base having concentric upwardly extending tubes the innertube being longer than the outer tube, and having radial outletperforations above the outer tube, a cap for the outer tube closing thespace between both tubes, a heating coil between the tubes, a motorsupported on the upper end of the inner tube and having a shaftextending therein and carrying an impeller for circulating a bath liquidthrough said inner tube.

4. A heating and circulating unit of the class described comprising asupporting base having concentric upwardly extending tubes the innertube being longer than the outer tube, and having radial outletperforations above the outer tube, a cap for the outer tube closing thespace between both tubes, a heating coil between the tubes, a motorsupported on the upper end of the inner tube and having a shaftextending therein and carrying an impeller for circulating a bath liquidthrough said inner tube, a bracket carried by said inner tube and havingmeans for holding a thermo-regulator in said bath at one side of saidunit.

CHARLES H. MILLER. PAUL SHERRICK.

